JP2000321161A - Capacitive vacuum sensor - Google Patents

Abstract

(57) [Problem] An object of the present invention is to suppress a measurement error due to a temperature change and improve the measurement accuracy of a sensor. According to the present invention, a pair of diaphragm electrodes and a fixed electrode facing each other with a space therebetween are disposed on a substrate, and pressure is measured from a change in capacitance between the diaphragm electrode and the fixed electrode facing the same. In the vacuum sensor, a temperature control unit for maintaining a constant temperature around the diaphragm electrode is provided on the substrate on which the diaphragm electrode and the fixed electrode are arranged, and a pressure detecting unit of the vacuum sensor is supported by a wire. The problem was solved by using a capacitance type vacuum sensor characterized by the above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type vacuum sensor for suppressing a measurement error caused by a temperature change and improving a measurement accuracy of the sensor.

[0002]

2. Description of the Related Art In the process of manufacturing electronic parts and semiconductor products, a process of forming or etching a thin film in a vacuum apparatus is indispensable. At this time, the process is usually performed while the pressure in the vacuum device is kept constant, but a capacitance type vacuum sensor is often used as a pressure measuring means in the vacuum device. FIG.
FIG. 1 shows an example of a conventional capacitive vacuum sensor with a temperature control function. The capacitance-type vacuum sensor has a chamber (reference pressure chamber 1) having a reference pressure inside the sensor, and the reference pressure chamber 1 is partitioned by a region 3 communicating with a vacuum device 2 and a diaphragm electrode 4. A fixed electrode 5 is arranged to face the diaphragm electrode 4 (elastic diaphragm). If there is a pressure difference between the reference pressure chamber 1 and the region 3 communicating with the vacuum device 2, the diaphragm electrode 4 is displaced in accordance with the pressure difference, but the capacitance between the diaphragm electrode 4 and the fixed electrode 5 , The electric information is transmitted to the electric circuit 7 through the conducting wire 9, the capacitance is converted into a voltage or a current, and output to the outside of the sensor, so that the pressure can be measured. However, because the diaphragm electrode 4 is displaced not only by the pressure in the vacuum device but also by the difference in the thermal expansion coefficients of the diaphragm electrode 4 and the surrounding materials, a slight displacement occurs in the diaphragm electrode 4 with a change in the temperature of the sensor. , Causing errors in pressure measurements. Therefore, in the conventional high-precision capacitive vacuum sensor, a heating unit 6 is provided inside to prevent a measurement error due to a temperature change while keeping the sensor temperature constant. However, the heating unit 6 has a diaphragm electrode. 4 and the fixed electrode 5 are heated from the outside so as to cover them, the temperature is measured by a temperature measuring unit 8 installed near the fixed electrode 5, and the whole inside of the sensor is kept at a constant temperature. A heat insulating material 10 is arranged outside the heating unit 6 to prevent heat of the heating unit 6 from being conducted to the sensor case 11 and becoming high in temperature.

[0003]

As a means for suppressing a measurement error due to a temperature change of the capacitance type vacuum sensor, the measurement accuracy of the sensor has been improved by heating and storing the inside of the sensor at a constant temperature. In principle, only the diaphragm electrode (elastic diaphragm) and fixed electrode inside the sensor and the supporting part that supports them are heated and kept uniformly, and the change in ambient temperature affects the mechanical deformation of these parts. If it does not, the problem of measurement error due to temperature change can be solved. However, in the conventional vacuum sensor, since these diaphragm electrodes (elastic diaphragms) and fixed electrodes are manufactured by mechanical processing, miniaturization and processing of complicated shapes are difficult. In order to heat and maintain the temperature, it is necessary to arrange a heating means so as to entirely cover them and to heat them from the outside. As a result, there is a problem that the heat capacity of the heated portion is increased, so that the temperature rise time becomes longer, and even when the sensor temperature is controlled to be constant, it is not possible to immediately respond to a sudden temperature change of the sensor. In addition, it takes several hours until a stable pressure measurement can be performed, so that much time and power are required.

[0004]

According to the present invention, there is provided a temperature control means for fixing a diaphragm electrode made of a conductive thin film having a small heat capacity to a substrate so as to face the fixed electrode and controlling the periphery of the diaphragm electrode to a constant temperature. Is provided to solve the above-mentioned conventional problem.

That is, according to the present invention, a pair of diaphragm electrodes and a fixed electrode facing each other with a space therebetween are arranged on a substrate,
In a vacuum sensor that measures pressure from a change in capacitance between the diaphragm electrode and an opposing fixed electrode, a constant temperature is maintained around the diaphragm electrode on the substrate on which the diaphragm electrode and the fixed electrode are arranged. A capacitance type vacuum sensor provided with a temperature control means for the same. In another invention, a pair of a diaphragm electrode and a fixed electrode opposed to each other with a space inside are arranged on a substrate, and pressure is measured from a change in capacitance between the diaphragm electrode and the fixed electrode opposed to the diaphragm electrode. In the vacuum sensor, a temperature control unit for controlling the temperature around the diaphragm electrode to a constant temperature is provided on the substrate on which the diaphragm electrode and the fixed electrode are arranged, and the pressure detection unit of the vacuum sensor is formed of a plurality of wires. It is a capacitance type vacuum sensor characterized by being supported. In the above,
The temperature control means is obtained by forming a heating layer and a temperature measurement layer on a substrate.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a method of the present invention wherein a plurality of regions are spatially partitioned by an elastic diaphragm (diaphragm electrode), and when the pressure in one or more of the partitioned regions changes, the diaphragm electrode is used. The diaphragm electrode is displaced in accordance with the pressure difference in the plurality of chambers partitioned by the above, and the amount of displacement is taken as a change in capacitance between the diaphragm electrode and a fixed electrode provided opposite to the diaphragm electrode. In a vacuum sensor for measuring pressure from now on, a heating unit and a temperature measuring unit are installed on a substrate on which the diaphragm electrode and the fixed electrode are formed, and the entire substrate on which the diaphragm electrode and the fixed electrode are formed. Is heated to control the temperature to be constant, and the periphery of the substrate on which the diaphragm and the fixed electrode are formed is made to have a heat insulating structure. It is characterized in that heat conduction to the periphery is suppressed, the temperature of the substrate on which the diaphragm electrode and the fixed electrode are formed is shortened, the temperature controllability is improved, and power consumption is reduced. This is a capacitance type vacuum sensor.

According to the present invention, the heating time is reduced,
By improving the temperature controllability, the accuracy of the sensor can be significantly improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
The capacitance-type vacuum sensor shown in FIG. 1 is manufactured by applying, for example, a semiconductor manufacturing process technology, and includes a pressure detection unit (mainly a structure in which a glass substrate 13 and a Si substrate 12 in the figure are combined. ) Is about several mm to several tens of mm, and the thickness is about 1 mm.

Reference numeral 2 in the figure denotes a vacuum device for measuring the internal pressure, which is a gauge port or a flange port (17 in the figure).
This vacuum sensor is attached to and used. Reference numeral 3 denotes a region communicating with the vacuum device 2, and the pressure in this region is substantially equal to the pressure of the vacuum device 2. Reference numeral 1 denotes a reference pressure chamber, and the Si substrate 12 on which the diaphragm electrode 14 is formed and the fixed electrode 1
5 is formed in a region sandwiched by the glass substrate 13 on which
Sealed to high vacuum pressure.

The diaphragm electrode 14 is connected to the vacuum device 2
When the pressure in the region 3 changes, the force for pressing the diaphragm electrode 14 also changes, and according to the amount of change, the diaphragm electrode 14
The distance between the fixed electrode 15 and the position facing the fixed electrode 15 is displaced.

The diaphragm electrode 14 and the fixed electrode 15
When a voltage is applied between the electrodes, the capacitance between the two electrodes is inversely proportional to the distance between the diaphragm electrode 14 and the fixed electrode 15, so that the pressure inside the vacuum device 2 It can be obtained from the capacity.

Here, the S electrode having the diaphragm electrode 14
The structure of the i-substrate 12 and the glass substrate 13 having the fixed electrode 15 will be described.

The Si substrate 12 having the diaphragm electrode 14 and the glass substrate 13 having the fixed electrode 15 are each composed of a silicon wafer having a thickness of 0.4 mm and a silicon wafer having a thickness of 1 m.
m Pyrex glass (manufactured by Corning Incorporated). However, the material is not limited as long as it is a material such as glass having the same or very close thermal expansion coefficient as that of the silicon wafer.

The diaphragm electrode 14 is usually easily formed by a technique such as dry etching used in fine processing in the semiconductor industry. Diaphragm electrode 14
Is 5 μm.

The fixed electrode 15 is usually formed by a thin film technique utilizing a vacuum such as sputtering or vapor deposition, and here uses A1 (aluminum).

The Si substrate 12 having the diaphragm electrode 14 and the glass substrate 13 having the fixed electrode 15 are finely processed so as to have a thickness of 7 μm between the two electrodes, and are bonded by an anodic bonding technique.

Next, the heat generation layer 16 and the temperature measurement layer 18 formed on the glass substrate 18 in the drawing will be described.

The heating layer 16 is made of, for example, a nichrome-based material.
It is made of a heat-generating material such as tantalum, and is uniformly formed directly on a substrate by a thin film technique utilizing vacuum such as sputtering or vapor deposition and a fine processing technique such as dry etching. The thickness of the heat generating layer 16 is about several μm, so that the space around the diaphragm electrode 14 is about 5 μm.
It is heated in a temperature range of 0 ° C to 200 ° C.

In order to measure the heating temperature, a resistor such as SiC utilizing the relationship between the resistance value and the temperature or a metal material utilizing the relationship between the thermoelectromotive force and the temperature is provided on the heating layer 16. A temperature measurement layer 18 is formed. The temperature measurement layer 18 is formed by the same thin film technology and fine processing technology as the heat generation layer 16, and has a structure that can be output to the electric circuit 7 via the conductive wire 9 and monitored. The conducting wire 9 also serves as a support for supporting the vacuum sensor.

The conductive wire 9 includes various conductive wires that come into contact with the fixed electrode 15, the heat generating layer 16, and the temperature measuring layer 18, and is therefore supported at at least three points. Further, since the length of the conductive wire 9 is several millimeters, it is approximately 1 mm.
0 mm square pressure detector (Si substrate 12 and glass substrate 13
) And have sufficient strength and stability against vibration and the like.

By adopting such a form, since there is no thermal influence from the surrounding structure other than the heat conduction through the conducting wire 9, the pressure detector fixed in a vacuum isolated form It will have an excellent heat insulation structure.

Therefore, in the capacitance type vacuum sensor according to the present invention, which is smaller and has a much smaller heat capacity than the conventional type,
The stabilization time for enabling pressure measurement is shortened and the temperature controllability is improved.

FIG. 3 shows the fluctuation of the output voltage of the pressure detector of the conventional capacitive vacuum sensor. The measurement is performed under a constant reduced pressure in order to eliminate the factor of the pressure change, and the heating temperature is set to 50
° C. The figure shows that the output voltage of the sensor should be constant and constant because there is no pressure change.However, after heating, the output voltage of the sensor is reduced due to thermal factors while reducing the amplitude of the vertical fluctuation. , It takes more than 2 hours to stabilize.

On the other hand, according to the capacitance type vacuum sensor of the present invention, the stabilization time is reduced to about 1/100, and the output voltage of the sensor becomes constant within about 2 minutes after heating. confirmed.

[0025]

According to the capacitive vacuum sensor with a temperature control function of the present invention, a sensor having a size of about several mm to several tens of mm and a thickness of about 1 mm can be realized. . Furthermore, since the sensor of the present invention is installed in a vacuum, heat radiation from the sensor is only heat conduction and heat radiation to a thin conductive wire or a dilute peripheral gas, so it has an excellent heat insulation structure and excellent heat retention. There are various effects. Therefore, the heat capacity of the sensor itself is much smaller than that of the conventional capacitive vacuum sensor, enabling heating with reduced power consumption, shortening the temperature rise time, and quick sensor temperature control in response to sudden sensor temperature changes. Thus, there is an effect that uniform heating can be performed without using a special mechanism.

[Brief description of the drawings]

FIG. 1 is an explanatory view in which a part of an embodiment of the present invention is omitted. FIG. 4 is an explanatory diagram of a structure of a conventional capacitance vacuum sensor. Similarly, the output voltage fluctuation graph.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Reference pressure chamber 2 Vacuum device 3 Area communicating with vacuum device 4, 14 Diaphragm electrode 5, 15 Fixed electrode 6 Heating unit 7 Electric circuit 8 Temperature measuring unit 9 Conductor 10 Insulation material 11 Sensor case 12 Si substrate 13 Glass substrate 16 Heating Layer 17 Flange port 18 Temperature measurement layer

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[Procedure amendment]

[Submission date] June 15, 1999 (1999.6.1
5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is an explanatory view in which a part of an embodiment of the present invention is omitted.

FIG. 2 is an explanatory view of the structure of a conventional capacitance vacuum sensor.

FIG. 3 is a graph showing a variation in output voltage.

[Description of Signs] 1 Reference pressure chamber 2 Vacuum device 3 Area communicating with vacuum device 4, 14 Diaphragm electrode 5, 15 Fixed electrode 6 Heating unit 7 Electric circuit 8 Temperature measuring unit 9 Conductor 10 Heat insulating material 11 Sensor case 12 Si substrate 13 Glass substrate 16 Heating layer 17 Flange port 18 Temperature measurement layer

Claims (3)

[Claims] 1. A vacuum for arranging a pair of diaphragm electrodes and a fixed electrode facing each other with a space therebetween on a substrate, and measuring pressure from a change in capacitance between the diaphragm electrode and the fixed electrode facing the vacuum electrode. In the sensor, a capacitance type vacuum sensor is provided on the substrate on which the diaphragm electrode and the fixed electrode are disposed, for controlling the temperature around the diaphragm electrode to be constant. 2. A vacuum in which a pair of diaphragm electrodes and a fixed electrode facing each other with a space therebetween are disposed on a substrate, and pressure is measured from a change in capacitance between the diaphragm electrode and the fixed electrode facing the vacuum electrode. In the sensor, a temperature control unit is provided on the substrate on which the diaphragm electrode and the fixed electrode are arranged to maintain a constant temperature around the diaphragm electrode, and a pressure detecting unit of the vacuum sensor is supported by a plurality of wires. A capacitance type vacuum sensor characterized in that: 3. The capacitance type vacuum sensor according to claim 1, wherein the temperature control means has a heat generating layer and a temperature measuring layer formed on the substrate.